Done a fair amount of beaver hunting over the years. Mostly spring, but some fall. As I near retirement, hoping to do some preseason (marten season) beaver hunting/trapping. Not wanting to use the old 22 lr. I don't have a 22 mag. And the wife's 17 hmr isn't my cup of tea. Debating loading down the 223. I have a 14.5 barrel AR. Bought some 69 gr. Sierras. Wondering if I can get them slow enough, 1900-2000 MV maybe, so there isn't too much damage to the front part of the animal. Also, it has to cycle the action.
Any experience, ideas.

I shot quite a few beaver with high power rifles-7.62 fmj is my favorite-head shots.
30-06 does the job too but you lose a size at auction.

The one time I used an 06 I wasn't satisfied with the end result. Saw some youtubes using the 6.5 Grendel. Appeared to work without much damage.

Slowing them down that much I'd be worried about cycling the AR, but I don't know much about ARs.

I get that you said you don't have a 22 magnum, but I prefer my 22 magnum to my 22LR for beaver. The extra speed seems to gives it a bit more forgiveness for less than perfectshots. Maybe just the excuse you need to buy another gun?

I prefer the 6.5 Grendel for hunting and .223 for plinking. You will not regret purchasing a Grendel hunter upper

I've got a 6.8 spc upper, actually 2, both rigged for hunting medium to large critters. The 223 with an 18 in. barrel will serve for any fur shooting. Would like a little more punch than the 22 mag for the same reason Ak Native said, forgiveness!
I loaded some 69 grainers but need to get to the range to shoot.

I"m with Aknative. .22 mag is perfect gun. It's not what ya shoot 'em with, it's where ya shoot 'em. an accurate shot is what really matters. Beaver is some good eating!

my experience with shooting beaver is the 22 mag is perfect. The bigger the exit hole the quicker they tend to sink IMO take a dip net along it will save you a lot of time and pain looking for ones that go under

Not sure about the .223 but a .22mag is just the ticket imo. I had a cousin who used .243 with home cast solid lead bullets on beaver and they had close to zero expansion.
Like the dip net Otterman recommended, a handy tool is a long willow with a large hook wired to one end like a gaff hook, barb squeezed down.

I have to agree . The 22 mag is by far the best medicine for this activity.

I am a big fan of the 22mag also. They tend to be tack driving accurate and pack a fair bit of a punch for their size. You should be able to do head shots all day with one.

I don’t have a 22 mag and not excited to buy a mostly one use gun.

I wouldn’t exactly call a 22 mag a one use gun. They’re awesome for a lot of stuff.

They Make a sub sonic reduced noise load now also. Makes the mag even more versatile. I’m thinking about using my 5 round spare clip loaded with these for dispatch and my 10 round for the bigger jobs.

I buy 40 grain FMJs by the carton. 22 Mag is my go to gun for bunnies and beavers. Id say ive shot 100+ wolves and 50+ wolverines with 22 mag over the years. very fur friendly with the FMJs. Pin hole in the hide. Im not saying its great for caribou but when youre close enough and have a steady hand it does the job just fine. Plus its just so much fun to shoot the mighty mouse 22

Yup, the Winchester 40gr FMJ is my go to for Coon hunting as well. Had some hollow points punch through the hide but then just trace in the fat instead of penetrating. Haven’t had a FMJ do that.

Well that settles it martentrapper. We’ve all decided that you’re buying a 22 magnum. Congratulations. You’re going to love it.

i'd ask the experts here if it was me https://www.ar15.com/forums/ar-15/
i have down loaded a .218 Bee for that purpose so cannot help too much.
But the guys on any black rifle forum, and there's several, probably can give ya load recipes as well.
Don't forget www.handloadersbench.com too. Bout my second favorite site besides Greybeards.

I'll second what Ryan mentioned I love my .22 mag I've used it to butcher more beef than you can imagine one and done in most cases unless you have to butcher a old range bull .
It's a favorite of many of my friend's for raccoons and or deer hunting on the reservation .
Another friend uses his to butcher buffalo on there ranch.
The 40 gr solid is a great round , the PMR30 a .22 mag pistol is super popular with the houndmen hunting mtn lions across the west.
Allan